Add a null check to areSelectionValuesReversed
Add a null check to areSelectionValuesReversed

See Microsoft/vscode#35601

xtermjs/xterm.js,akalipetis/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,akalipetis/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js